<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>

    <link rel="stylesheet" type="text/css" href="styles.css">
</head>
<body>

    <div class="container1">
            <div class="item a1">

            </div>

            <div class="item b1">

            </div>

            <div class="item c1">
            
            </div>
    </div>

    <!-- 水平跟垂直都居中 -->
    <div class="container2" style="display: flex;height: 200px;">
        <div style="background-color: aquamarine;width: 100px;height: 100px; margin: auto;"></div>

    </div>
    
</body>
</html>